Columnar downhole gas separator and method of use

ABSTRACT

A gas separator is provided including a tapered portion, the “bell section” and a wide portion, the “shroud.” The bell section resides on the lower end of the gas separator where it attaches to the production pipe. The shroud is substantially larger in diameter than the production pipe and allows mixed fluid and gas to enter through an open top. 
     The gas separator is attached at the string of production pipe, so that some of the production pipe extends below the gas separator. A section of production pipe that is covered by the gas separator is perforated. Gas bubbles are removed from the mixed fluid by gravity, abrupt changes in direction, and perforations that restrict the flow area of the fluid.

FIELD OF THE INVENTION

This invention relates generally to gas separators. More particularly, the invention relates to gas separators suspended above the bottom of a production well and used to separate mixed fluid that consists of gas bubbles suspended in liquid.

BACKGROUND OF THE INVENTION

Generally, fluid produced from a well must be pumped to the surface. Most of these fluids are mixed, consisting of gas bubbles suspended within the fluid. Gas passing through a pump reduces the efficiency of the pump and increases the cost to produce the fluid from the well. In extreme circumstances, large quantities of gas can create “gas lock” within the pump. “Gas lock” prevents fluid from being displaced, effectively stopping production and potentially damaging the pump. Therefore, it is considered desirable to separate the gas from the fluid. Pumping fluid substantially free from gas prevents the aforementioned problems and results in lower production costs.

Separation of gas bubbles from a mixed fluid may be based on the geometry of the inlet holes as the mixed fluid enters the gas separator. Additionally, a second stage of separation may be utilized whereby the fluid is pumped to the surface from a distance below the gas separator. In a second stage of separation, the fluid is pumped to the surface through a gas anchor which passes concentrically through the production pipe and is attached to the pump. This allows gravity to operate on the gas bubbles remaining in the fluid. Thus, the fluid pumped to the surface has a reduced concentration of gas bubbles and is more efficient to pump.

A difficulty with gas separators that operate at or produce fluid from the lower end of the production pipe is “silting in.” Often the fluid produced in wells includes silt and heavy particles that fall out of the fluid as the fluid is pumped to the surface. As the silt and heavy particles accumulate, the inlet to the pump or the perforations in a gas separator may become blocked. Blockage of the pump inlet or gas separator leads to a reduction or complete stoppage of fluid production. The gas separator, along with the entire string of production pipe, must be removed from the well and cleared of silt and heavy particles. “Silting in” results in additional costs both as a result of removing the gas separator from the well and from time spent without production from the well.

Most prior art gas separators are placed within the production pipe, effectively reducing the area of the production pipe. This reduction in area corresponds to a reduction in the amount of fluid that may be pumped through the production pipe. Many gas separators that are larger in area than the production pipe require additional centrifugal or submersible pumps to operate.

Those gas separators that are larger in area than the production pipe and do operate without any additional pumps or equipment are prone to “silting in.” One such gas separator is disclosed in U.S. Pat. No. 1,554,842 to Coulter. This gas separator is larger in diameter than the production pipe and attaches to the lowest end of the production pipe string. The gas separator encloses a perforated section of the production pipe located at the lowest end of the production pipe string. Fluid flows into the open top of the gas separator. The fluid enters the perforated section of the production pipe and is pulled to the surface through a pump. The perforated section is located at the lowest point of the string of production pipe. The pump inlet is located just above the perforated section. Thus, any silt or heavy particles that do not pass through the pump build up in the closed end of the gas separator. As silt builds up in the gas separator, the perforations in the production pipe are blocked and the volume of fluid produced is reduced. Eventually, all of the perforations are blocked or the production of fluid is reduced to the point where the gas separator must be removed from the well and the silt removed.

Another such gas separator is disclosed in U.S. Pat. No. 4,241,788 to Brennan. This gas separator operates in a similar manner, with multiple cups each having perforations on the bottom to allow fluid to enter the production pipe. A gas anchor is attached to the pump and passes concentrically through the production pipe. Fluid is pumped through the gas anchor at the lowest end of the production string. The end of the production pipe is enclosed by a gas separator with vents that allow gas to pass outside to the well. Similar to the Coulter gas separator, this gas separator is subject to “silting in.” The gas anchor is enclosed by the gas separator. This allows any silt or heavy particles, which do not flow through the pump, to build up eventually blocking the inlet to the gas anchor and stopping production.

Therefore, a need exists for a gas separator that operates based on the flow produced by the production pump, minimizes the reduction in area of the production pipe, and maximizes time in production by preventing silt and heavy particles from obstructing the perforations of the gas separator or the inlet to the pump.

SUMMARY OF INVENTION

The present invention addresses the need to separate mixed fluid in a production well into gas and a gas bubble free fluid. The present invention reduces the amount of gas that remains in a fluid when it reaches the pump. Reduction of gas enables the pump to operate more efficiently without locking-up. In addition, the present invention enables the gas separator to remain in the production well for a longer period of time. Often, the fluid in a production well contains silt and heavy particles that separate from the fluid as it is pumped to the surface. The portion of the production pipe that extends below the gas separator allows the sediment to gather in the lower portion of the production pipe without blocking or “silting-in” the perforations that allow fluid flow.

The present invention consists of a tapered portion, the “bell section” and a wide portion, the “shroud.” The bell section resides on the lower end of the gas separator where it attaches to the production pipe. The shroud is substantially larger in diameter than the production pipe and allows mixed fluid and gas to enter through an open top.

The present invention attaches to a string of production pipe that is lowered down a well. The gas separator is attached at some point in the middle of the string of production pipe, so that some of the production pipe extends below the gas separator. A section of production pipe that is covered by the gas separator is perforated. The fluid in the well is a mixed fluid that consists of fluid and gas bubbles. Initially, the mixed fluid rises in the well. Some gas bubbles continue to rise and are separated as the fluid changes direction and enters the open top of the gas separator. Gravity continues to act on the fluid causing further gas bubble separation as the mixed fluid is drawn down the length of the gas separator. The perforations in the production pipe cause the velocity of the fluid to increase, resulting in additional separation of gas bubbles from the fluid. The fluid, which has been separated from some gas bubbles, gathers in the production pipe. As this fluid continues downward to the opening of the gas anchor, gravity continues to operate, separating additional gas bubbles. As the additional bubbles separate, they rise and exit through the perforations in the production tubing and ultimately the open top of the gas separator. Thus, the fluid that enters the gas anchor and is ultimately pumped to the surface has a greatly reduced amount of gas bubbles. This allows the pump to operate more efficiently, with less chance of locking-up due to a gas pocket in the pump.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description of the preferred embodiments presented below, reference is made to the accompanying drawings.

FIG. 1 is a side view of a preferred embodiment of the present invention.

FIG. 2 is a side view of a second preferred embodiment of the present invention, where the invention consists of two separate pieces joined together.

FIG. 3 is a cross section view of a preferred embodiment of the present invention. The invention has been cut-away to show a preferred method of attachment to the production pipe.

FIG. 4 is a cross section view of the gas separator during the upstroke of the pump. The flow of mixed fluid is shown. The mixed fluid travels through the gas separator and is produced as fluid without gas bubbles after passing through the gas separator.

FIG. 5 is a cross section view of the gas separator during the downstroke of the pump. The escape of the gas bubbles is shown. The mixed fluid travels through the gas separator and gas bubbles are separated from the mixed fluid and escape through the perforated production pipe and the open top of the gas separator

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the descriptions that follow, like parts are marked throughout the specification and drawings with the same numerals, respectively. The drawing figures are not necessarily drawn to scale and certain figures may be shown in exaggerated or generalized form in the interest of clarity and conciseness.

With Respect to FIG. 1, gas separator 110 is supported by a bell collar 130. Bell collar 130 is a cylindrical shape designed to support the gas separator by attaching to production pipe (not shown). Taper 170 is an angle between the bell collar 130 and the shroud 190. Shroud 190 causes mixed fluid to enter the gas separator 110 through the top opening 150 of the gas separator 110.

FIG. 2 shows the preferred embodiment of gas separator 110. Gas separator 110 consists of three pieces; a bell section 210, a collar 290, and a shroud 230. Shroud 230 has external threads 270. Additionally, the bell section 210 has bell collar 130. Bell collar 130 attaches to production pipe (not shown). Shroud 230 is substantially larger in diameter than production pipe and has external threads 270. Shroud 230 and bell section 210 are connected by collar 290. Collar 290 has internal threads (not shown).

FIG. 3 shows the preferred method of attaching gas separator 110 to production pipes 350 and 370. Production pipes 350 and 370 are externally threaded at the ends 390. Gas separator 110 is supported by bell collar 130. Bell collar 130 is internally threaded 330 to accept the threaded ends 390 of production pipes 350 and 370. Additionally, production pipe 370 contains perforations 360. While the perforations may extend for any length along production pipe 370, the perforations in the preferred embodiment stop approximately 12 inches before the upper end gas separator 110, but the distance may be varied depending on well conditions.

FIG. 4 shows the preferred method of production using gas separator 110. Gas separator 110 is attached to production pipe string 480, such that some of production pipe string 480 extends below gas separator 110. Gas separator 110 and pipe string 480 reside in a production well. The production well consists of well casing 410 having vents 420. Vents 420 allow mixed fluid 430 (fluid combined with gas bubbles) to enter well casing 410.

Gas anchor 450 is attached to pump 440 and suspended concentrically in production pipe string 480. In the preferred embodiment, gas anchor 450 extends 10 to 15 feet below gas separator 110.

In use, gas separator 110 is attached to production pipes 350 and 370 as shown in FIG. 3. The 2⅜-inch diameter production pipes 350 and 370 pass through gas separator 110 and thread into bell collar 130. Additional sections of production pipe are added above production pipe 370 as gas separator 110 is lowered into position in a production well as shown in FIG. 4. Preferred embodiments of gas separator 110 include pipes having a 4½ inch to a 12⅝ inch outside diameter and lengths of approximately 7 feet. However, length and diameter of the gas separator may be adjusted to individual well size and fluid consistency.

Referring to FIG. 4, the mixed fluid 430 rises due to pressure, either natural or artificial. The pressure causes mixed fluid 430 to rise until it meets gas separator 110. The mixed fluid 430 decreases velocity as it encounters taper 130 and shroud 190. As mixed fluid 430 loses velocity, gravity continues to act on gas bubbles causing them to be released from mixed fluid 430.

Pump 440 reduces the pressure below gas separator 110, at the end of gas anchor 450. The reduction in pressure causes mixed fluid 490 to enter gas separator 110. Gravity continues to act on the mixed fluid 490, allowing the gas bubbles 491 to rise. The change in direction of mixed fluid 490 combined with gas bubbles 491 rising due to gravity acting on the mixed fluid 490 causes further separation between the fluid 490 and gas bubbles 491 located therein. As the mixed fluid 490 continues downward in gas separator 110, gravity continues to separate the mixed fluid 490 and gas bubbles 491. The mixed fluid 490 continues downward passing through perforations 360 into production pipe string 480. Again, the abrupt change of direction causes a separation of gas bubbles 492 from the mixed fluid 490. As the mixed fluid 490 continues downward in production pipe string 480, gravity continues acting on the gas bubbles 493 causing them to separate from the mixed fluid 490. The fluid that has a greatly reduced concentration of gas bubbles 494 again has an abrupt change of direction as it enters gas anchor 450 and begins travelling upward to pump 440. The fluid that enters gas anchor 450 has a much reduced concentration of gas bubbles from the original mixed fluid 430.

Silt or heavy particles that entered gas separator 110 in mixed fluid 490 may fall rather than pass upward through the gas anchor 450. Gas anchor 450 is suspended above the lowest end of production pipe string 480, which may be closed. This allows silt and heavy particles 470 to accumulate without blocking or “silting-in” gas anchor 450 or perforations 360.

The majority of gas bubbles escape the gas separator 110 during the downstroke of pump 440, as shown in FIG. 5. The flow of fluid separated from gas bubbles 494 is suspended during the downstroke of pump 440. Gas bubbles 491 escape through the open top 150 of gas separator 110. Gas bubbles 492 that are separated from the fluid 490 at perforations 360 rise and escape through top opening 150 of gas separator 110. Gas bubbles 493 that are separated after perforations 360 rise through perforations 360 and ultimately top opening 150 during the downstroke of pump 440.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the following claims. 

1. An apparatus to separate gas bubbles from a production fluid comprising: a bell collar having a means to concentrically attach a gas separator to a production pipe string; the production pipe string having a set of perforations and extending below the bell collar; a circular shroud having a first diameter extending above the bell collar; the shroud having a top opening with a second diameter; and, wherein the gas separator covers the set of perforations.
 2. The apparatus of claim 1 wherein the top opening is beveled.
 3. The apparatus of claim 1 wherein the second diameter is larger than the first diameter.
 4. The apparatus of claim 1 further comprising a gas anchor located inside the production pipe string below the gas separator.
 5. The apparatus of claim 4 wherein the gas anchor extends below the bell collar.
 6. The apparatus of claim 5 wherein the production pipe string is closed below the gas anchor.
 7. The apparatus of claim 6 wherein the gas anchor does not extend to the bottom of the production pipe string.
 8. The apparatus of claim 1 wherein the gas separator is comprised of a bell section removably connected to a shroud section.
 9. A gas separator comprising: a bell collar; the bell collar having a gas separator concentrically attached to production pipe string; a gas anchor located inside the production pipe string; the gas anchor extending below the bell collar; the production pipe string extending below the gas separator; the production pipe string being closed on the lower end; a shroud extending above the bell collar; the shroud having a top opening; the gas separator covering a set of perforations in the production pipe string.
 10. The apparatus of claim 9 wherein the gas anchor does not extend to the lowest end of the production pipe string.
 11. A method for separating gas bubbles from a mixed fluid, composed of fluid with gas bubbles suspended therein, comprising the steps of: providing a plurality of sections of production pipe having a first diameter; providing a gas separator with a top opening, the gas separator further comprising a bell collar and a shroud section with a top opening and a second diameter larger than the first diameter; providing a set of perforations in the production pipe; connecting the bell collar to the production pipe with the top opening facing upward; connecting the production pipe within the gas separator, adjacent to the set of perforations; lowering the production pipe and the gas separator into the mixed fluid; separating gas bubbles from the mixed fluid as the mixed fluid flows through the gas separator and the plurality of sections of production pipe.
 12. The method of claim 1 1 further comprising: providing a section of production pipe with a closed end below the gas separator.
 13. The method of claim 11 further comprising: providing a pump; attaching the pump to the production pipe string; separating the gas bubbles from the mixed fluid by lowering pressure in at least one section of production pipe from the plurality of sections of production pipe with the pump, thereby causing the mixed fluid to rise.
 14. The method of claim 13 further comprising: concentrically passing a gas anchor through the production pipe string; attaching the gas anchor to the pump; raising the fluid through the gas anchor with the pump.
 15. The method of claim 14 further comprising: positioning a section of production pipe of the plurality of sections of production pipe below the gas anchor.
 16. The method of claim 14 wherein: providing a section of production pipe of the plurality of sections of production pipe with a closed end below the gas separator.
 17. The method of claim 16 further comprising: bottoming a section of the production pipe of the plurality of section of production pipe in a well.
 18. The method of claim 16 further comprising: positioning the gas anchor above the closed end whereby a set of sediment particles that have accumulated in the production pipe are prevented from obstructing a flow of mixed fluid into the gas anchor.
 19. The method of claim 11 further comprising extending a section of production pipe of the plurality of sections of production pipe below the gas separator. 